ANATOMY

Detailed explanation-1: -An echo is a sound caused by the reflection of sound waves from a surface back to the listener. It is the reflection of sound, arriving at the listener sometime after the direct sound. Basically a reflection of sound causes echo.

Detailed explanation-2: -An echo is a repetition or a partial repetition of a sound due to REFLECTION. REVERBERATION is also reflected sound, but in this case, separate repetitions of the original sound are not distinguishable.

Detailed explanation-3: -When a sound wave (longitudinal wave) occurs on a flat and hard surface, it reflects back. This phenomenon of reflection of sound is called echo.

Detailed explanation-4: -Ordinarily echo is not heard as the reflected sound gets merged with the original sound.